TFT Substrate Passivation Structure for Contact Area and Etch Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for fabricating thin film transistor (TFT) array substrates face challenges in increasing the driving margin and ensuring a sufficiently large contact area between conductive materials, which can lead to over-etching of the gate insulating layer and damage to data interconnection lines, resulting in reduced manufacturing efficiency and increased costs.
Innovation Solution
A TFT substrate design that includes a gate interconnection line, a semiconductor layer, and passivation layers with a porous lattice structure, where the outer sidewalls of the second passivation layer are positioned inside the outer sidewalls of the first passivation layer, allowing for controlled etching and preventing over-etching, while maintaining a large contact area for easy lift-off and reducing damage to data interconnection lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the passivation film is over-etched to form a sufficiently large undercut under the photoresist pattern, then the contact area between the photoresist stripper and the photoresist pattern is increased, but the gate insulating layer is over-etched and its thickness becomes non-uniform, reducing the driving margin
Solution Approach 1:
The passivation film is divided into two separate layers: a first passivation layer (dense structure) and a second passivation layer (porous lattice structure). The second layer is specifically designed to be over-etched during the lift-off process, creating the necessary undercut for photoresist stripper contact, while the first layer remains protected and maintains its original thickness to preserve the driving margin.
Solution Approach 2:
Different regions of the passivation structure are given different etching characteristics. The second passivation layer has a porous lattice structure that makes it more susceptible to over-etching, while the first passivation layer has a dense structure that resists over-etching. This local differentiation allows selective removal where needed while protecting critical areas.
2Area of stationary object
If the passivation film is over-etched to form an undercut, then the contact area is increased for better lift-off, but the data interconnection line is damaged by over-etching, causing contact failure
Solution Approach 1:
The passivation structure is segmented into two layers with different protective functions. The first passivation layer acts as a protective barrier over the data interconnection line, preventing damage during over-etching of the second layer, while still allowing the second layer to provide the necessary undercut for lift-off contact.
Solution Approach 2:
The first passivation layer is deposited beforehand to provide a protective cushion over the data interconnection line. This protective layer prevents direct damage to the data line during the over-etching process, ensuring contact reliability while still allowing the second layer to be over-etched for adequate lift-off contact area.
3Ease of manufacture
If a single passivation layer is used, then the manufacturing process is simpler, but it cannot simultaneously provide sufficient undercut for lift-off and protect the gate insulating layer from over-etching
Solution Approach 1:
The single passivation layer is segmented into two functional layers: the first passivation layer provides protection against over-etching, while the second passivation layer provides the porous structure that enables controlled over-etching for undercut formation. This segmentation allows both functions to coexist.
Solution Approach 2:
The two-layer passivation structure achieves multi-functionality: the first layer serves as a protective barrier, the second layer serves as an etchable undercut-forming layer, and together they provide both protection and adequate contact area for lift-off, making the structure adaptable to multiple requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the driving margin, prevents over-etching of the gate insulating layer, and ensures a reliable contact area between conductive materials, thereby improving manufacturing efficiency and reducing costs by preventing damage to data interconnection lines.
Implementation Method 1
the second passivation film has more porous lattice structure than that of the first passivation layer
Data Source
AI summary
A thin film transistor (TFT) substrate is provided in which a sufficiently large contact area between conductive materials is provided in a contact portion and a method of fabricating the TFT substrate. The TFT substrate includes a gate interconnection line formed on an insulating substrate, a gate insulating layer covering the gate interconnection line, a semiconductor layer arranged on the gate insulating layer, a data interconnection line including a data line, a source electrode and a drain electrode formed on the semiconductor layer, a first passivation layer formed on the data interconnection line and exposing the drain electrode, a second passivation layer formed on the first passivation film and a pixel electrode electrically connected to the drain electrode. An outer sidewall of the second passivation layer is positioned inside an outer sidewall of the first passivation layer.